Solution:

0.5

Explanation:
Rachel Age = 10.5
Diana Age = 0.5
10.5 + 0.5 = 11

Many must have guessed the answer as 1.

Solution:

See the figure for the answer. Wasn't it a bit tricky?

Solution:

We now have a square of 3x3 size, 2 squares of 2x2 size and 5 squares of 1x1 size.

Solution:

The figure tells that B is located to the North-East of E.

Solution:

60 minutes

Explanation:
Roy will be able to consume all the five tablets in an hour.

Tablet 1 will be taken in 0 min.
Tablet 2 will be taken in 15 min.
Tablet 3 will be taken in 30 min.
Tablet 4 will be taken in 45 min.
Tablet 5 will be taken in 60 min.

Solution:

Sam : 2
Dean : 5
Castiel : 7

Age diff
7 - 2 = '5' is prime
7 - 5 = '2' is prime
5 - 2 = '3' is prime

Solution:

3 1 2 2 1 1
1 3 1 1 2 2 2 1

Read Line as one 1 => 1
Read Line 2 as two one => 2 1
Read Line 3 as one two and one one => 1 2 1 1
and so on.

Solution:

If you see the picture, they formed a pentagonal shape and achieved the required.

Solution:

I + IX = X

The equation read from the other side becomes X = XI + I which is false.

Solution:

The Lady sitting in the chair has the detector attached to the back of her blouse.

Solution:

What is the correct time ?